Wooden timbers such as those to be used for railroad ties are cured and treated to enhance their structural integrity and serviceability. Standards for treating and curing railroad ties have been adopted, an example of such standards being those set forth in the Manual for Railway Engineering provided by AREMA, the American Railway Engineering and Maintenance-of-way Association. AREMA requires that outer surface of railroad ties be perforated or incised during the curing process in order to reduce checking or splitting of the ties. Such incising is to be performed in a specified pattern of perforations.
Incisors having driven drums with protruding teeth are often utilized to perform the incising tasks. Some incising drums utilize cutting teeth that are clamped or bolted onto the drum assembly. Teeth in such drum assemblies are often bent, broken or lost during the incising process. Drum having bent, broken or lost incising teeth will produce irregular or unwanted incising patterns. Replacement of these teeth is time consuming and expensive and increases the cost of the incising process.
Other incising drum combinations such as that described in U.S. Pat. No. 4,137,956 to Toberg are comprised of a plurality of individual annular tooth rings separated by one of more spacer rings. The tooth rings described in Toberg have outwardly extending angularly equi-spaced teeth. The tooth rings and spacer rings are fixed on a central core to form the incising drum by means of a keyway located on each tooth ring and a key that fits into the central core. The keyway is positioned on the ring at one-quarter of the angle between adjacent teeth on the tooth ring. The tooth rings are arranged on the central core so that the teeth of every other tooth ring are offset from the teeth of its adjacent tooth ring by one-half of a tooth spacing by rotating every other tooth ring. Multiple spacer rings are utilized to adjust the spacing between adjacent tooth rings.
To assemble the tooth ring drum of Toberg for incising timber in a desired pattern, many individual tooth rings and spacer rings must be utilized. This presents a disadvantage when tooth rings must be replaced during maintenance of the incisor drum. The individual tooth rings must be placed in a particular order in order to achieve the desired spacing. The disassembly and re-assembly of the many tooth and spacer rings in the desired configuration increases the time and therefore the cost of the drum maintenance.
Another disadvantage of Toberg is that the fixed angular position of the keyway on the tooth rings limits the amount of adjustment and variation that can be made to the array of teeth on the drum form from such rings. This in turn limits the adjustments that can be made to points of incising on the timber as it is drawn through an incising machine.
Consequently, a need exist for improvements in drum incisor configuration that will allow for the incising of timber in a desired pattern, reduce the incidence of bent, broken or lost incisor teeth, and reduce the time associated with drum maintenance.